U.S. patent number 10,770,426 [Application Number 16/327,856] was granted by the patent office on 2020-09-08 for micro device transferring method, and micro device substrate manufactured by micro device transferring method.
This patent grant is currently assigned to CENTER FOR ADVANCED META-MATERIALS. The grantee listed for this patent is CENTER FOR ADVANCED META-MATERIALS. Invention is credited to Byung Ik Choi, Seong Min Hong, Yun Hwangbo, Bong Kyun Jang, Yeon Woo Jeong, Jae Hyun Kim, Kwang Seop Kim, Kyung Sik Kim, Hak Joo Lee.
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United States Patent |
10,770,426 |
Hwangbo , et al. |
September 8, 2020 |
Micro device transferring method, and micro device substrate
manufactured by micro device transferring method
Abstract
A method for transferring a micro device, includes: a
compression step in which a carrier film having a micro-device
attached to an adhesive layer thereof is brought into contact with
a substrate comprising a solder deposited on metal electrodes
formed on the substrate and is compressed on the substrate; a first
adhesive strength generation step in which the solder disposed
between the micro-device and the metal electrodes is compressed in
the compression step to generate first adhesive strength between
the micro-device and the solder; a second adhesive generation step
in which the micro-device is bonded to the adhesive layer through
press-fitting in the compression step to generate second adhesive
strength between the micro-device and the adhesive layer; and a
release step in which the carrier film is separated from the
substrate, with the micro-device adhered to the solder.
Inventors: |
Hwangbo; Yun (Daejeon,
KR), Choi; Byung Ik (Daejeon, KR), Kim; Jae
Hyun (Daejeon, KR), Jeong; Yeon Woo (Daejeon,
KR), Hong; Seong Min (Daejeon, KR), Jang;
Bong Kyun (Daejeon, KR), Kim; Kwang Seop
(Daejeon, KR), Kim; Kyung Sik (Daejeon,
KR), Lee; Hak Joo (Daejeon, KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
CENTER FOR ADVANCED META-MATERIALS |
Daejeon |
N/A |
KR |
|
|
Assignee: |
CENTER FOR ADVANCED
META-MATERIALS (Daejeon, KR)
|
Family
ID: |
1000005044083 |
Appl.
No.: |
16/327,856 |
Filed: |
August 21, 2017 |
PCT
Filed: |
August 21, 2017 |
PCT No.: |
PCT/KR2017/009082 |
371(c)(1),(2),(4) Date: |
March 26, 2019 |
PCT
Pub. No.: |
WO2018/038481 |
PCT
Pub. Date: |
March 01, 2018 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20190259728 A1 |
Aug 22, 2019 |
|
Foreign Application Priority Data
|
|
|
|
|
Aug 24, 2016 [KR] |
|
|
10-2016-0107759 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
24/16 (20130101); H01L 25/0753 (20130101); H01L
24/32 (20130101); H01L 24/81 (20130101); H01L
33/62 (20130101); H01L 21/677 (20130101); H01L
21/768 (20130101); H01L 24/83 (20130101); H01L
21/52 (20130101); H01L 21/18 (20130101); H01L
24/13 (20130101); H01L 2224/81192 (20130101); H01L
2224/16227 (20130101); H01L 2224/13111 (20130101); H01L
2224/13113 (20130101); H01L 2224/83052 (20130101); H01L
2933/0066 (20130101); H01L 2224/13139 (20130101); H01L
2224/83898 (20130101); H01L 2224/81201 (20130101); H01L
2924/12041 (20130101); H01L 2224/32059 (20130101); H01L
2924/014 (20130101); H01L 2224/83201 (20130101); H01L
2224/81801 (20130101); H01L 2224/81005 (20130101) |
Current International
Class: |
H01L
21/00 (20060101); H01L 21/18 (20060101); H01L
21/52 (20060101); H01L 21/677 (20060101); H01L
25/075 (20060101); H01L 33/62 (20100101); H01L
23/00 (20060101); H01L 25/00 (20060101); H01L
21/768 (20060101); H01L 33/00 (20100101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
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|
4891895 |
|
Mar 2012 |
|
JP |
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10-2009-0132931 |
|
Dec 2009 |
|
KR |
|
10-2011-0118616 |
|
Oct 2011 |
|
KR |
|
10-2013-0116648 |
|
Oct 2013 |
|
KR |
|
Other References
International Search Report for PCT/KR2017/009082 dated Nov. 24,
2017 from Korean Intellectual Property Office. cited by
applicant.
|
Primary Examiner: Minskey; Jacob T
Assistant Examiner: Hoover; Matthew
Attorney, Agent or Firm: Revolution IP, PLLC
Claims
The invention claimed is:
1. A micro-device transfer method comprising: a compression step in
which a carrier film having a micro-device attached to an adhesive
layer thereof is brought into contact with a substrate comprising a
solder deposited on metal electrodes formed on the substrate and is
compressed on the substrate; a first adhesive strength generation
step in which the solder disposed between the micro-device and the
metal electrodes is compressed in the compression step to generate
first adhesive strength between the micro-device and the solder; a
second adhesive generation step in which the micro-device is bonded
to the adhesive layer through press-fitting in the compression step
to generate second adhesive strength between the micro-device and
the adhesive layer; and a release step in which the carrier film is
separated from the substrate, with the micro-device adhered to the
solder, wherein the second adhesive strength is proportional to a
press-fitting depth of the micro-device press-fitted into the
adhesive layer and the press-fitting depth of the micro-device in
the adhesive layer is determined within a range allowing the second
adhesive strength to be less than the first adhesive strength.
2. The micro-device transfer method according to claim 1, wherein
the adhesive layer has a smaller thickness than a critical
press-fitting depth of the micro-device at which the second
adhesive strength proportional to the press-fitting depth of the
micro-device press-fitted into the adhesive layer becomes larger
than the first adhesive strength.
3. The micro-device transfer method according to claim 1, wherein
at least one of compressive force applied to the carrier film on
the substrate in the compression step, a viscoelastic coefficient
of the adhesive layer and yield strength of the adhesive layer is
regulated such that the second adhesive strength proportional to
the press-fitting depth of the micro-device press-fitted into the
adhesive layer becomes less than the first adhesive strength.
4. The micro-device transfer method according to claim 3, wherein
the adhesive layer has a greater thickness than a critical
press-fitting depth of the micro-device at which the second
adhesive strength proportional to the press-fitting depth of the
micro-device press-fitted into the adhesive layer becomes larger
than the first adhesive strength.
5. The micro-device transfer method according to claim 1, wherein,
in the release step, release force for separating the carrier film
from the substrate is sequentially applied from one side to the
other side with reference to the micro-device such that the carrier
film is sequentially separated from the micro-device from one side
of a region in which the micro-device is bonded to the adhesive
layer to the other side thereof.
6. The micro-device transfer method according to claim 5, wherein
the carrier film is disposed to surround a cylindrical roller and
the release force for separating the carrier film from the
substrate is sequentially applied to the micro-device by rotation
of the roller about a rotational axis of the roller.
7. The micro-device transfer method according to claim 5, wherein
the carrier film is formed in a platen shape and the release force
for separating the carrier film from the substrate is sequentially
applied to the micro-device by applying the release force to one
side of the carrier film.
8. A micro-device substrate manufactured by the micro-device
transfer method according to claim 1.
Description
TECHNICAL FIELD
The present invention relates to a micro-device transfer method and
a micro-device substrate manufactured by the same and, more
particularly, to a micro-device transfer method, which allows
micro-devices to be transferred to a substrate without an
additional process for enhancing adhesive strength, and a
micro-device substrate manufactured by the same.
BACKGROUND ART
In general, a display using micro-light emitting diodes
(micro-LEDs) is spotlighted as an advanced next generation display
capable of replacing existing displays in the art. For manufacture
of such a micro-LED display, a technique for transferring each LED
to a modularized circuit board is needed.
In a typical method for transferring micro-LEDs to solders on a
circuit board, the micro-LEDs are transferred one by one by a
vacuum chuck. However, this method requires a very long time in
manufacture of a display having a very large number of pixels, such
as HD, UHD, SUHD, and the like. In addition, as the size of the
devices decreases, this method has a problem of difficulty in
handling devices such as micro-LEDs using the vacuum chuck used in
an existing process.
Therefore, although there is a need for a technique for
transferring a large number of micro-LEDs at the same time, such a
technique has not been developed in the art and there is difficulty
in the manufacturing process.
In order to solve such a problem, a roll transfer process can be
used. However, this process has a problem in that roll transfer of
micro-devices is very difficult to achieve due to very low adhesive
strength of solder pastes when the micro-devices are transferred to
a substrate using typical solder pastes.
DISCLOSURE
Technical Problem
It is an aspect of the present invention to provide a micro-device
transfer method, which allows transfer of micro-devices to a
substrate without an additional process for enhancing adhesive
strength by regulating adhesive strength through control of a
press-fitting depth of the micro-devices on a carrier film, and a
micro-device substrate manufactured by the micro-device transfer
method.
Technical Solution
In accordance with one aspect of the present invention, a
micro-device transfer method includes: a compression step in which
a carrier film having a micro-device attached to an adhesive layer
thereof is brought into contact with a substrate including a solder
deposited on metal electrodes formed thereon and is compressed on
the substrate; a first adhesive strength generation step in which
the solder disposed between the micro-device and the metal
electrodes is compressed in the compression step to generate first
adhesive strength between the micro-device and the solder; a second
adhesive generation step in which the micro-device is bonded to the
adhesive layer through press-fitting in the compression step to
generate second adhesive strength between the micro-device and the
adhesive layer; and a release step in which the carrier film is
separated from the substrate, with the micro-device adhered to the
solder, wherein the second adhesive strength is proportional to a
press-fitting depth of the micro-device press-fitted into the
adhesive layer and the press-fitting depth of the micro-device in
the adhesive layer is determined within a range allowing the second
adhesive strength to be less than the first adhesive strength.
The adhesive layer may have a smaller thickness than a critical
press-fitting depth of the micro-device at which the second
adhesive strength proportional to the press-fitting depth of the
micro-device press-fitted into the adhesive layer becomes larger
than the first adhesive strength.
At least one of compressive force applied to the carrier film on
the substrate in the compression step, a viscoelastic coefficient
of the adhesive layer and yield strength of the adhesive layer may
be regulated such that the second adhesive strength proportional to
the press-fitting depth of the micro-device press-fitted into the
adhesive layer becomes less than the first adhesive strength.
The adhesive layer may have a greater thickness than a critical
press-fitting depth of the micro-device at which the second
adhesive strength proportional to the press-fitting depth of the
micro-device press-fitted into the adhesive layer becomes larger
than the first adhesive strength.
In the release step, release force for separating the carrier film
from the substrate may be sequentially applied from one side to the
other side with reference to the micro-device such that the carrier
film can be sequentially separated from the micro-device from one
side of a region in which the micro-device is bonded to the
adhesive layer to the other side thereof.
The carrier film may be disposed to surround a cylindrical roller
and the release force for separating the carrier film from the
substrate may be sequentially applied to the micro-device by
rotation of the roller about a rotational axis of the roller.
The carrier film may be formed in a platen shape and the release
force for separating the carrier film from the substrate may be
sequentially applied to the micro-device by applying the release
force to one side of the carrier film.
In accordance with another aspect of the present invention, there
is provided a micro-device substrate manufactured by the
micro-device transfer method as set forth above.
Advantageous Effects
A micro-device transfer method according to the present invention
and a micro-device substrate manufactured by the same have the
following effects.
First, a process of continuously transferring a large number of
micro-devices to a target substrate through combination of a roller
and a platen can be advantageously achieved.
Second, the micro-devices can be advantageously transferred to the
substrate using adhesive strength generated by mechanical
deformation between the micro-devices, a carrier film and solders,
instead of using adhesive strength chemically regulated by a
typical method in the art.
DESCRIPTION OF DRAWINGS
FIG. 1 is a flow diagram of a micro-device transfer method
according to one embodiment of the present invention.
FIG. 2 shows a micro-device and a carrier film before a compression
step of the micro-device transfer method of FIG. 1.
FIG. 3 shows the micro-device and the carrier film after the
compression step of the micro-device transfer method of FIG. 1.
FIG. 4 is a view depicting a relationship between press-fitting
depth and adhesive strength of the micro-device with respect to the
carrier film in the micro-device transfer method of FIG. 1.
FIG. 5 is a view illustrating a critical press-fitting depth of the
micro-device in the micro-device transfer method of FIG. 1.
FIG. 6 is a view illustrating the carrier film in the micro-device
transfer method of FIG. 1.
FIG. 7 is a view of a modification of the carrier film of FIG.
6.
FIG. 8 is a view illustrating a principle of a release step of the
micro-device transfer method of FIG. 1.
FIG. 9 is a view illustrating the release step of the micro-device
transfer method of FIG. 1.
FIG. 10 is a view illustrating a modification of the release step
of FIG. 9.
FIG. 11 is a picture showing micro-devices having a smaller
press-fitting depth than a critical press-fitting depth and
transferred to a substrate.
FIG. 12 is a picture showing micro-devices having a smaller
press-fitting depth than a critical press-fitting depth and not
transferred to a substrate.
BEST MODE
Hereinafter, embodiments of the present invention will be described
with reference to the accompanying drawings. In description of the
following embodiments. Like components will be denoted by like
reference numerals throughout the specification and portions
irrelevant to the description will be omitted for clarity.
Herein, when a layer, a film, a region, a sheet or the like is
referred to as being disposed "on" another layer, film, region,
sheet or the like, it may be directly on the other layer, film,
region, sheet or the like, or intervening elements or layers may be
present. In addition, when an element is referred to as being
disposed "on" another element, this means that the element is
disposed on or under the other element and does not means that the
element is necessarily disposed on the other element with reference
to the direction of gravity.
Herein, the terms "comprises," "comprising," "including," and
"having," are inclusive and therefore specify the presence of
stated features, elements, and/or components, but do not preclude
the presence or addition of one or more other features, elements,
and/or components, unless specifically stated otherwise. It should
be understood that the drawings are not to precise scale and may be
exaggerated in thickness of lines or size of components for
descriptive convenience and clarity only and the present invention
is not limited thereto.
Referring to FIG. 1 to FIG. 12, the following description will be
given of a micro-device transfer method according to one embodiment
of the present invention and a micro-device substrate manufactured
by the same.
As shown in FIG. 1 to FIG. 12, the micro-device transfer method
according to the embodiment of the present invention includes a
compression step S10, a first adhesive strength generation step
S20, a second adhesive generation step S30, and a release step
S40.
First, as shown in FIG. 2, a carrier film 10 including a
micro-device 20 attached thereto and a substrate 50 including a
solder 30 deposited on metal electrodes formed on the substrate 50
are prepared and aligned such that the micro-device 20 can be
brought into contact with the solder 30.
As the carrier film 10 is moved toward the substrate 50, the
micro-device 20 is brought into contact with the metal electrodes
40. The solder 30 is deposited on the metal electrodes 40 to
enhance adhesive strength between the metal electrodes 40 and the
micro-device 20. The metal electrodes 40 are disposed on the
substrate 50 to supply electric power to the micro-device 20 and
may be formed of gold (Au).
The carrier film 10 includes an adhesive layer 12 to which the
micro-device 20 is attached and a base film 11 supporting the
adhesive layer 12 such that the micro-device 20 can be press-fitted
into the adhesive layer 12 by pressure applied to the carrier film
10 through the micro-device 20 in the compression step S10.
In the compression step S10, the carrier film 10 having the
micro-device 20 attached to the adhesive layer 12 is brought into
contact with the substrate 50 having the solder 30 deposited on the
metal electrodes 40 and is compressed thereon.
The adhesive layer 12 may be formed of a previously cured UV
curable adhesive material, such as SOG, PMMA, Su-8, and the
like.
The solder 30 is provided in the form of pastes including solder
balls 31 and a flux 32 surrounding the solder balls 31 while
fluidly moving, in which the solder balls 31 may be composed of
silver (Ag), tin (Sn), or bismuth (Bi) alloys.
In the first adhesive strength generation step S20, the solder 30
disposed between the micro-device 20 and the metal electrodes 40 is
compressed in the compression step S10 to generate first adhesive
strength F.sub.1 between the micro-device 20 and the solder 30.
In the first adhesive strength generation step S20, the solder
balls 31 are deformed from a spherical shape to an elliptical shape
by pressure applied thereto in the compression step S10.
In the second adhesive generation step S30, the micro-device 20 is
press-fitted into and bonded to the adhesive layer 12 in the
compression step S10 to generate second adhesive strength F.sub.2
between the micro-device 20 and the adhesive layer 12.
Here, the second adhesive strength F2 is proportional to a
press-fitting depth of the micro-device 20 in the adhesive layer
12.
Specifically, a contact area between the adhesive layer 12 and an
edge of the micro-device 20 increases with increasing press-fitting
depth of the micro-device 20 in the adhesive layer 12, thereby
causing increase in friction between the adhesive layer 12 and the
micro-device 20.
Next, a relationship between the press-fitting depth and adhesive
strength of the micro-device 20 with respect to the adhesive layer
12 will be described with reference to FIG. 4.
In FIG. 4(a), the press-fitting depth of the micro-device 20 in the
adhesive layer 12 is denoted by d.sub.a, and in FIG. 4(b), the
press-fitting depth of the micro-device 20 in the adhesive layer 12
is denoted by d.sub.b, which is greater than d.sub.a.
Adhesive strength F.sub.2b between the micro-device 20 having a
press-fitting depth d.sub.b and the adhesive layer 12 is larger
than adhesive strength F.sub.2a between the micro-device 20 having
a press-fitting depth d.sub.a and the adhesive layer 12, since the
contact area between the adhesive layer 12 having a press-fitting
depth d.sub.b and the edge of the micro-device 20 is larger than
the contact area between the adhesive layer 12 having a
press-fitting depth d.sub.a and the edge of the micro-device 20 to
generate larger friction.
Accordingly, the second adhesive strength F.sub.2 is proportional
to the press-fitting depth of the micro-device 20.
Here, the adhesive strength F.sub.2b between the micro-device 20
having a press-fitting depth d.sub.b and the adhesive layer 12 and
the adhesive strength F.sub.2a between the micro-device 20 having a
press-fitting depth d.sub.a and the adhesive layer 12 are indicated
by wave patterns in FIG. 4.
In the release step S40, with the micro-device 20 bonded to the
solder 30, the carrier film 10 is separated from the substrate
50.
Here, in order to allow the micro-device 20 to be separated from
the adhesive layer 12 with the micro-device 20 bonded to the solder
30, it is desirable that the second adhesive strength F.sub.2 be
less than the first adhesive strength F.sub.1.
Referring to FIG. 5, a critical press-fitting depth enabling easy
separation of the micro-device 20 from the adhesive layer 12 will
now be described.
Referring to FIG. 5(a), when the press-fitting depth of the
micro-device 20 in the adhesive layer 12 is d.sub.1, which is less
than the critical press-fitting depth d.sub.c, the second adhesive
strength F.sub.2 between the adhesive layer 12 and the micro-device
20 is less than the first adhesive strength F.sub.1 between the
solder 30 and the micro-device 20.
In this case, when the carrier film 10 is separated from the
substrate 50, the micro-device 20 is separated from the carrier
film 10, with the micro-device 20 bonded to the solder 30.
Referring to FIG. 5(b), when the press-fitting depth of the
micro-device 20 in the adhesive layer 12 is d.sub.2, which is
greater than the critical press-fitting depth d.sub.c, the second
adhesive strength F.sub.2 between the adhesive layer 12 and the
micro-device 20 is greater than the first adhesive strength F.sub.1
between the solder 30 and the micro-device 20.
In this case, when the carrier film 10 is separated from the
substrate 50, the micro-device 20 is moved together with the
carrier film 10 in a state in which the micro-device 20 attached to
the carrier film 10.
That is, the critical press-fitting depth means a boundary
press-fitting depth at which the second adhesive strength F.sub.2
becomes larger than the first adhesive strength F.sub.1 and a
relative magnitude of the second adhesive strength F.sub.2 with
respect to the first adhesive strength F.sub.1 may be regulated
using the critical press-fitting depth.
As shown in FIG. 6, the adhesive layer 12 is formed to a thickness
t.sub.1 less than the critical press-fitting depth in order to
prevent the micro-device 20 from reaching the critical
press-fitting depth d.sub.c.
As the adhesive layer 12 is formed to have a smaller thickness than
the critical press-fitting depth d.sub.c, the second adhesive
strength F.sub.2 is always less than the first adhesive strength
F.sub.1 even when the micro-device 20 is press-fitted into the
carrier film 10 by the thickness of the adhesive layer 12.
Accordingly, it is possible to generate the second adhesive
strength F.sub.2 to be less than the first adhesive strength
F.sub.1 without regulating properties of the adhesive layer 12 for
regulation of the press-fitting depth of the micro-device 20, such
as viscoelastic coefficient of the adhesive layer 12, yield
strength of the adhesive layer 12, and the like, compressive force
with respect to the carrier film 10 and the substrate 50, and the
like.
On the other hand, as shown in FIG. 7, the thickness t.sub.2 of the
adhesive layer 12 may be greater than the critical press-fitting
depth d.sub.c.
As the adhesive layer 12 is formed to a greater thickness than the
critical press-fitting depth d.sub.c, the press-fitting depth of
the micro-device 20 can become greater than the critical
press-fitting depth and the second adhesive strength F.sub.2 can
become larger than the first adhesive strength F.sub.1 depending
upon the press-fitting depth of the micro-device 20, thereby
causing a problem in the course of separating the micro-device 20
from the carrier film 10.
In order to prevent this problem, the second adhesive strength F2
becomes less than the first adhesive strength F1 by regulating the
compressive force applied in the compression step S10.
In addition, in order to generate the second adhesive strength
F.sub.2 to be less than the first adhesive strength F.sub.1, the
viscoelastic coefficient of the adhesive layer 12 may be
regulated.
Specifically, in order to guarantee that the second adhesive
strength F.sub.2 generated between the adhesive layer 12 and the
micro-device 20 is less than the first adhesive strength F.sub.1
generated between the solder 30 and the micro-device 20, the
adhesive layer 12 may be formed of a material having a high
viscoelastic coefficient.
Further, in order to generate the second adhesive strength F.sub.2
to be less than the first adhesive strength F.sub.1, yield strength
of the adhesive layer 12 may be regulated.
When compressive force applied in the compression step S10
increases above an elastic limit of the adhesive layer 12, elastic
deformation can occur in the course of press-fitting the
micro-device 20 into the adhesive layer 12. Here, if the adhesive
layer 12 has relatively low yield strength, the press-fitting depth
of the micro-device 20 is relatively increased by the compressive
force exceeding the elastic limit of the adhesive layer 12, thereby
causing generation of the second adhesive strength F.sub.2 larger
than first adhesive strength F.sub.1.
Thus, the yield strength of the adhesive layer 12 may be regulated
to become large such that the micro-device 20 can be press-fitted
to a relatively small depth into the adhesive layer 12 by the
compressive force exceeding the elastic limit of the adhesive layer
12, whereby the second adhesive strength F2 can become less than
the first adhesive strength F1.
As described above, in order to generate the second adhesive
strength F.sub.2 to be less than the first adhesive strength
F.sub.1, the compressive force applied in the compression step S10,
the viscoelastic coefficient of the adhesive layer 12, and the
yield strength of the adhesive layer 12 may be regulated
individually or in combination.
In the release step S40, the micro-device 20 may be sequentially
separated from the adhesive layer 12 from one side of a bonded
region therebetween to the other side thereof.
When the entirety of the micro-device 20 is separated from the
carrier film 10 at the same time under a condition that the
difference between the first adhesive strength F.sub.1 and the
second adhesive strength F.sub.2 is not large, there is a
possibility that some micro-devices 20 remain on the carrier film
10 in the release step.
To prevent this problem, release force for separating the carrier
film 10 from the substrate is sequentially applied from one side of
the carrier film 10 to the other side thereof with reference to the
micro-device 20.
As the release force is sequentially applied to the micro-device
20, the second adhesive strength F.sub.2 is dispersed in the
release step S40, whereby the second adhesive strength
corresponding to the first adhesive strength is reduced, thereby
allowing the micro-device 20 to be more easily separated from the
adhesive layer 12.
As shown in FIG. 9, release of the carrier film 10 may be performed
through coupling with a roller R in the release step S40.
Specifically, the carrier film 10 is disposed to surround a
cylindrical roller R and the carrier film 10 is sequentially
compressed on the substrate 50 by rotation of the roller R about a
rotational axis of the roller R to generate the first adhesive
strength F.sub.1 and the second adhesive strength F.sub.2.
Thereafter, the release force for separating the micro-device 20
from the adhesive layer 12 is sequentially applied to the
micro-device 20 by rotation of the roller R, thereby enabling
separation of the micro-device 20 from the adhesive layer 12.
It should be understood that the present invention is not limited
thereto and the carrier film 10 may have a platen shape as shown in
FIG. 10.
Thus, the carrier film 10 having a platen shape is compressed on
the substrate 50 to generate the first adhesive strength F.sub.1
and the second adhesive strength F.sub.2, and the release force
F.sub.s for separating the micro-device 20 from the adhesive layer
12 is applied to one side of the carrier film 10.
Here, the release force F.sub.s is sequentially applied to the
micro-device 20.
As a result, the micro-device 20 can be advantageously transferred
to the substrate 50 using adhesive strength generated by mechanical
deformation between the micro-device 20, the carrier film 10, and
the solder 30, instead of using adhesive strength chemically
regulated by a typical method in the related art.
Thus, the micro-device 20 can be more conveniently and stably
transferred to the substrate 50 using the difference between the
first adhesive strength and the second adhesive strength generated
in the compression step S10 only through the process of separating
the micro-device 20 from the adhesive layer 12.
FIG. 11 shows a state in which the micro-device 20 having a smaller
press-fitting depth d.sub.1 than the critical press-fitting depth
d.sub.c is transferred to the substrate 50.
In the structure wherein the micro-device 20 has a smaller
press-fitting depth d.sub.1 than the critical press-fitting depth
d.sub.c, since the second adhesive strength F.sub.2 between the
adhesive layer 12 and the micro-device 20 is less than the first
adhesive strength F1 between the solder 30 and the micro-device 20,
the micro-device 20 is transferred to the substrate 50 to be
attached to the solder 30.
FIG. 11 shows a press-fitting trace of the micro-device 20
separated from the adhesive layer 12 at a press-fitting location 13
on the adhesive layer 12 into which the micro-device 20 is
press-fitted, and it can be seen that, since the micro-device 20
has a smaller press-fitting depth d.sub.1 than the critical
press-fitting depth d.sub.c, there is substantially no
press-fitting trace.
FIG. 12 shows a state in which the micro-device 20 having a greater
press-fitting depth d.sub.2 than the critical press-fitting depth
d.sub.c is transferred to the substrate 50.
In the structure wherein the micro-device 20 has a greater
press-fitting depth d.sub.2 than the critical press-fitting depth
d.sub.c, since the second adhesive strength F.sub.2 between the
adhesive layer 12 and the micro-device 20 is larger than the first
adhesive strength F1 between the solder 30 and the micro-device 20,
the micro-device 20 remains on the adhesive layer 12, instead of
being transferred to the substrate 50.
FIG. 12 shows a press-fitting trace of the micro-device 20
separated from the adhesive layer 12 at a press-fitting location 14
on the adhesive layer 12 into which the micro-device 20 is
press-fitted, and it can be seen that, since the micro-device 20
has a greater press-fitting depth d.sub.2 than the critical
press-fitting depth as described above, a clear press-fitting trace
of the micro-device remains on the adhesive layer.
Although some embodiments have been described herein, it should be
understood that these embodiments are provided for illustration
only and are not to be construed in any way as limiting the present
invention, and that various modifications, changes, alterations,
and equivalent embodiments can be made by those skilled in the art
without departing from the spirit and scope of the present
invention.
INDUSTRIAL APPLICABILITY
The present invention has industrial applicability in the technical
field of transferring micro-devices to a substrate without an
additional process for enhancing adhesive strength.
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